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Evap leak at breather on filler neck? Might have to dig deeper...

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bmdubya1198
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Evap leak at breather on filler neck? Might have to dig deeper...

Post by bmdubya1198 »

I finally decided to smoke test my car for the P0455 code that never goes away. The only place I could see anything escaping was this breather piece on the filler neck, which (if I'm not mistaken) should be a vent. I'm not sure if it should be closed off with a check valve of some sort, so please correct me if I'm wrong here. I'm going to try to investigate this further.
I couldn't see any leaks coming from the top of the tank, but that doesn't necessarily mean I wasn't missing anything. A hose could have been pinched when I installed the tank, since it's only been in place for a few months now and the code has been present since then.
The evap/fuel tank setup on this car is from my '98 V70 GLT, so that's the evap system I'm working with, with the charcoal canister mounted near the fuel filter. I added smoke to the system through the vacuum tee at the fuel pressure regulator, which is next to the filter (not the same setup as the '98 GLT). Yeah, I know, it's a bastardized setup, but electronically it's the same as the 2000 V70R should expect. I will also check for function of the evap components on VIDA, but I'm expecting everything to function properly.

Anyway the point of this thread, can anybody confirm that I should see leakage at this breather when smoke testing the evap system? I would think that the car would pick this up as a leak, but as I mentioned, it might be blocked off with a check valve.
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Post by RickHaleParker »

bmdubya1198 wrote: 27 Oct 2021, 10:12 Anyway the point of this thread, can anybody confirm that I should see leakage at this breather when smoke testing the evap system? I would think that the car would pick this up as a leak, but as I mentioned, it might be blocked off with a check valve.
A breather would open when the tank pressure is less the atmospheric pressure, to prevent a vacuum when fuel is being pumped out. If you are pumping pressure into the tank you would expect it to be closed. If it does not close when the tank is pressurized it would fail Leak diagnostics. Leak diagnostics work by sealing off the tank and measuring how fast the pressure drops.

Look in VIDA for a fuel tank pressure measurement. That measurement would be a very useful diagnostic tool.
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Post by bmdubya1198 »

Tank pressure bounces between 0 and 0.25. At idle, it stays closer to 0.25, occasionally bouncing high when I look at the graph. When I tried to test the evap close valve (next to the fuel filter), it didn't do anything. Voltage at the connector checks out, and resistance is exactly the correct spec, 17 ohms. I have a feeling that the valve may be bad.
When I checked my 2000 S70, it activates when I manually activate it on VIDA.
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Post by RickHaleParker »

bmdubya1198 wrote: 27 Oct 2021, 12:09 When I tried to test the evap close valve (next to the fuel filter), it didn't do anything. Voltage at the connector checks out, and resistance is exactly the correct spec, 17 ohms. I have a feeling that the valve may be bad.
You mean the Canister Purge Valve ? Which is connected to the EVAP canister.
The Canister Purge Valve is normally closed and it opens when the ECM grounds it. That is it is switched on the ground side not the supply side. The ECM opens the CPV when the EVAP canister needs to be purged of fuel. The EVAP canister is there to collect and store fuel vapors when the engine is not running. Then purge the stored vapors to the engine when the engine is running.

Can you get the Volvo part number off the valve your messing with. That way we can determine if you are in the right place or not.
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Post by scot850 »

I am trying to remember how the FWD system works. I am probably wrong, but if I recall correctly, the pipe to that vent comes from the roll over valve? So if that is correct, then the roll-over valve should be shut when the emissions test is running and that would make any valve up there immaterial to the P0455.

It could be the roll-over valve that is not working. That is where Vida should help as Rick suggests.

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Post by bmdubya1198 »

It could be what you're referring to as the rollover valve/leak detection pump, part number 9486016. #9 in this diagram https://www.volvopartswebstore.com/show ... evel=24667

I ran to the junkyard earlier this afternoon and grabbed one, that's definitely working now. However when I run the test in VIDA (under fault tracing for the code) it still shows a rough leak. Looking at the graph, there should be no fuel tank pressure with everything open, and it bounces back and forth between 0 and the peak.
I noticed while running this test that when the canister purge valve closed, the car stumbled very slightly. May be normal, or it could possibly be a vacuum leak on that hose. I couldn't see one yesterday while testing, but I'm going to check again anyway.

I'll post the log and the code description below.
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Post by bmdubya1198 »

And just to add it in, a diagram of the evap system.
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Post by RickHaleParker »

Leak Diagnostics is carried out as follows:
1. The EVAP canister shut-off valve and canister purge (CP) valve are closed and the fuel tank system is now completely closed. Note: Canister shut-off valve is normally open (Turned off, not grounded ). Canister purge valve is normally open (Turned off, not grounded ). To close both you ground the canister shut-off valve only.

2. Pressure in the fuel tank should be stable. If pressure drops the canister purge (CP) valve is leaking.
Note: this assumes the rest of the system is tight. It could be the hose to the (CP)

3. The EVAP canister shut-off valve opens, the tank system is open. The canister purge (CP) valve is pulsed and because of the negative pressure in the intake manifold the engine starts to suck air through the EVAP canister. Because the EVAP canister shut-off valve is open the pressure in the fuel tank drops slowly. If the pressure in the fuel tank drops rapidly the EVAP canister shut-off valve is clogged.
Note:If the canister shut-off valve/vent is clear, Air will be sucked through the canister vent. If the canister vent is clogged Air will be sucked out of the fuel tank. Path of least resistance.

4. The EVAP canister shut-off valve is closed, the canister purge (CP) valve continued to be pulsed, pressure in the fuel tank should drop rapidly. If pressure does not drop enough there is a large leakage in the fuel tank system. A diagnostic trouble code (DTC) will be stored.
Note: Fails if it sucking air from somewhere other then the tank. This is ECM-4308

5. The canister purge (CP) valve is closed, the EVAP canister shut-off valve is still closed, there is negative pressure in the fuel tank. The negative pressure (A) in the fuel tank has stabilized, if pressure starts to increase too quickly, this indicates a small leakage in the system. A diagnostic trouble code (DTC) is stored.

6. The EVAP canister shut-off valve opens, the EVAP function is enabled and the diagnostic test is finished.

To carry out the diagnostic: ( Test conditions ).
engine coolant temperature (ECT) is between -10OC and +107OC.
no permanent faults stored.
engine idling.
speed must be 0 km/h.
the concentration of fuel vapor in the canister must not be too high.
there must be more than 11 liters of fuel in the tank
the pressure in the fuel tank must not be too high.
fuel trim must be active.
the car must be below 2700 meters above sea level.

The diagnostic test starts at the earliest 17 minutes after the engine has been started when all conditions have been met. It takes approximately 30 seconds.
Last edited by RickHaleParker on 28 Oct 2021, 03:49, edited 2 times in total.
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Post by RickHaleParker »

Because you are getting ECM-4308, Large leak #4 above. Disconnect the hose between the Fuel tank and the Canister at the Canister end. Inject the smoke into that hose. Look for leaks in the tank system.

The Values can be checked with a vacuum pump and a 12V Voltage source. The Vacuum pump from a brake bleeding kit will work.
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1998 C70, B5234T3, 16T, AW50-42, Bosch Motronic 4.4, Special Edition package.
2003 S40, B4204T3, 14T twin scroll AW55-50/51SN, Siemens EMS 2000.
2004 S60R, B8444S TF80 AWD. Yamaha V8 conversion
2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0.

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Post by bmdubya1198 »

Great info! I'll try that today and see what I can find. It's gotta be one of the hoses above the tank that's leaking, since there is nothing else that I can find wrong here.
00 V70R Venetian Red/Charcoal M56 Swapped 207k
07 XC90 V8 AWD Sport Titanium Grey/Black 202k
92 245 White/Beige 249k
91 944 Turbo 175k
03 BMW X5 3.0i
01 330Ci
99 528iT
84 318i
Sold-
03 S60 2.4T
00 S70 GLT
98 V70 GLT
93 944
98 S90
95 850 GLT
01 S60 2.4T
05 S60R M66
08 S40 2.4i
88 744 Turbo M46

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